let _Vue = null;
export default class VueRouter {
  static install(Vue) {
    //1 判断当前插件是否被安装
    if (VueRouter.install.installed) {
      return;
    }
    VueRouter.install.installed = true;
    //2 把Vue的构造函数记录在全局
    _Vue = Vue;
    //3 把创建Vue的实例传入的router对象注入到Vue实例
    // _Vue.prototype.$router = this.$options.router
    _Vue.mixin({
      beforeCreate() {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;
        }
      },
    });
  }
  constructor(options) {
    this.options = options;
    this.routeMap = {};
    // observable
    this.data = _Vue.observable({
      current: "/",
    });
    this.init();
  }
  init() {
    this.createRouteMap();
    this.initComponent(_Vue);
    this.initEvent();
  }
  createRouteMap() {
    //遍历所有的路由规则 吧路由规则解析成键值对的形式存储到routeMap中
    this.options.routes.forEach((route) => {
      this.routeMap[route.path] = route.component;
    });
  }
  initComponent(Vue) {
    Vue.component("router-link", {
      props: {
        to: String,
      },
      render(h) {
        return h(
          "a",
          {
            attrs: {
              href: this.to,
            },
            on: {
              click: this.clickhander,
            },
          },
          [this.$slots.default]
        );
      },
      methods: {
        clickhander(e) {
          if (self.options.mode === "hash") {
            window.location.hash = `#${this.to}`;
          } else {
            history.pushState({}, "", this.to);
          }
          this.$router.data.current = this.to;
          e.preventDefault();
        },
      },
      // template:"<a :href='to'><slot></slot><>"
    });
    const self = this;
    Vue.component("router-view", {
      render(h) {
        // self.data.current
        const cm = self.routeMap[self.data.current];
        return h(cm);
      },
    });
  }
  initEvent() {
    // history
    window.addEventListener("popstate", () => {
      this.data.current = window.location.pathname;
    });

    // hash
    window.addEventListener("hashchange", () => {
      // console.log("hashchange", this.getHash());
      this.data.current = this.getHash() || "/";
    });
  }

  // copy from vue-router
  getHash() {
    // We can't use window.location.hash here because it's not
    // consistent across browsers - Firefox will pre-decode it!
    let href = window.location.href;
    const index = href.indexOf("#");
    // empty path
    if (index < 0) return "";

    href = href.slice(index + 1);
    // decode the hash but not the search or hash
    // as search(query) is already decoded
    // https://github.com/vuejs/vue-router/issues/2708
    const searchIndex = href.indexOf("?");
    if (searchIndex < 0) {
      const hashIndex = href.indexOf("#");
      if (hashIndex > -1) {
        href = decodeURI(href.slice(0, hashIndex)) + href.slice(hashIndex);
      } else href = decodeURI(href);
    } else {
      href = decodeURI(href.slice(0, searchIndex)) + href.slice(searchIndex);
    }

    return href;
  }
}
